Insight Guru Inc.
10/20/2026 | Press release | Distributed by Public on 10/19/2026 22:39
S&P 500 Movers | Winners: WDC, SNDK, DDOG | Losers: MOS, NRG, AMP
On Monday, October 19, the S&P 500 rose 0.4%, the Nasdaq-100 rallied 1.2% and the Dow Jones Industrial Average dipped 0.1%. Over the past week the S&P 500 is down 1.5%, and over the past month it is up 0.5%.
Decliners outnumbered gainers 324 to 176 within the S&P 500. At the extremes, Western Digital (WDC) gained 6.1% and Mosaic (MOS) fell 4.8%.
Monday's S&P 500 Winners
The 10 S&P 500 stocks with the highest returns on Monday:
| # | Ticker | Company Name |
1-D Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | WDC | Western Digital | 6.1% | 104.7% |
| 2 | SNDK | SanDisk | 5.5% | 477.6% |
| 3 | DDOG | Datadog | 5.4% | 91.5% |
| 4 | TWLO | Twilio | 5.3% | 80.9% |
| 5 | AMZN | Amazon.com | 5.0% | 13.7% |
| 6 | PLTR | Palantir Technologies | 4.4% | 9.2% |
| 7 | MRNA | Moderna | 4.1% | n/a |
| 8 | MRVL | Marvell Technology | 4.1% | 179.5% |
| 9 | TSLA | Tesla | 3.8% | -18.2% |
| 10 | MPWR | Monolithic Power Systems | 3.5% | 39.0% |
Monday's S&P 500 Losers
And the 10 S&P 500 stocks with the lowest returns on Monday:
| # | Ticker | Company Name |
1-D Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | MOS | Mosaic | -4.8% | -23.6% |
| 2 | NRG | NRG Energy | -4.2% | -37.0% |
| 3 | AMP | Ameriprise Financial | -4.1% | -1.1% |
| 4 | ES | Eversource Energy | -3.5% | -0.9% |
| 5 | HONA | Honeywell Aerospace | -3.3% | n/a |
| 6 | FLEX | FLEX | -3.2% | 44.9% |
| 7 | CEG | Constellation Energy | -3.0% | -25.2% |
| 8 | DHI | D.R. Horton | -2.9% | -5.2% |
| 9 | BG | Bunge Global | -2.9% | 17.9% |
| 10 | GPC | Genuine Parts | -2.8% | 8.8% |
Which Of Monday's Movers Were Already On A Run?
Mosaic (MOS) appears on both the one-day and one-month losers lists. It fell 4.8% on Monday and is down 26.8% over the past month; excluding Monday, it had already lost 23.1% over the other sessions.
Moderna (MRNA) added to a longer run: after Monday's 4.1% gain, the stock is up 47.3% over the past month, and it was already up 41.5% before Monday.
The 3.2% decline in FLEX on Monday was not a one-off: the stock is down 19.3% over the past month, and down 16.6% over the sessions before Monday.
Movers Over The Last Week
Widening the window to five trading days, these are the strongest and weakest names in the S&P 500:
Winners
| # | Ticker | Company Name |
1-W Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | CTSH | Cognizant Technology Solutions | 11.9% | -18.1% |
| 2 | ACN | Accenture | 11.2% | -8.6% |
| 3 | CSGP | CoStar | 8.9% | -52.7% |
| 4 | BRO | Brown & Brown | 8.8% | -12.5% |
| 5 | EXPE | Expedia | 8.7% | 3.6% |
| 6 | DRI | Darden Restaurants | 8.3% | 21.2% |
| 7 | AJG | Arthur J. Gallagher | 8.2% | -1.3% |
| 8 | BALL | BALL | 7.9% | 21.7% |
| 9 | ERIE | Erie Indemnity | 7.6% | -13.5% |
| 10 | EFX | Equifax | 7.6% | -26.3% |
Losers
| # | Ticker | Company Name |
1-W Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | FLEX | FLEX | -25.3% | 44.9% |
| 2 | HPE | Hewlett Packard Enterprise | -20.6% | 135.4% |
| 3 | SMCI | Super Micro Computer | -19.7% | 9.7% |
| 4 | COHR | Coherent | -19.4% | 25.7% |
| 5 | P | Everpure | -18.2% | n/a |
| 6 | AMAT | Applied Materials | -17.0% | 61.3% |
| 7 | LITE | Lumentum | -16.2% | 126.4% |
| 8 | CIEN | Ciena | -15.0% | 47.2% |
| 9 | AKAM | Akamai Technologies | -14.2% | 0.0% |
| 10 | PANW | Palo Alto Networks | -14.1% | 88.4% |
Movers Over The Last Month
And over the last 21 trading days, the strongest and weakest names in the S&P 500:
Winners
| # | Ticker | Company Name |
1-M Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | MRNA | Moderna | 47.3% | n/a |
| 2 | PTC | PTC | 42.1% | 10.8% |
| 3 | ACN | Accenture | 31.7% | -8.6% |
| 4 | P | Everpure | 22.0% | n/a |
| 5 | VEEV | Veeva Systems | 21.7% | 41.9% |
| 6 | CCL | Carnival Corporation | 21.1% | -12.0% |
| 7 | SNPS | Synopsys | 18.1% | -3.2% |
| 8 | MTD | Mettler-Toledo International | 16.8% | 16.6% |
| 9 | CASY | Casey's General Stores | 16.1% | 25.8% |
| 10 | TJX | TJX Companies | 15.8% | -3.2% |
Losers
| # | Ticker | Company Name |
1-M Returns |
YTD Returns |
|---|---|---|---|---|
| 1 | COHR | Coherent | -26.9% | 25.7% |
| 2 | MOS | Mosaic | -26.8% | -23.6% |
| 3 | MGM | MGM Resorts International | -24.7% | -22.0% |
| 4 | SNDK | SanDisk | -23.5% | 477.6% |
| 5 | STX | Seagate Technology | -23.0% | 140.7% |
| 6 | ARE | Alexandria Real Estate Equities | -22.6% | -13.3% |
| 7 | WDC | Western Digital | -20.2% | 104.7% |
| 8 | HOOD | Robinhood Markets | -19.4% | -14.7% |
| 9 | FLEX | FLEX | -19.3% | 44.9% |
| 10 | GEN | Gen Digital | -18.5% | -11.7% |
Volatility Is The Cost Of Owning Stocks. Concentration Makes It A Bill
Every name on these lists made a move big enough to notice. A diversified holder reads that as noise; a concentrated holder feels it as real money. The difference is not the stock, it is the portfolio around it.
Building that portfolio is what the Trefis High Quality (HQ) Portfolio does: roughly 30 businesses with the cash generation and balance-sheet strength to absorb bad days, selected and rebalanced by rules. It has a track record of outpacing a benchmark that combines the S&P 500, the S&P MidCap 400, and the Russell 2000. Let the movers list remind you why diversification exists.
Insight Guru Inc. published this content on October 20, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on October 20, 2026 at 04:39 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]